1. Technical Field
The present invention relates to a method of manufacturing a wiring board (substrate).
2. Related Art
In recent years, there has been more demand than ever before for the demand for electronic equipment including portable equipment typified by, e.g., mobile telephones to be provided in higher-density packaging. In order to respond to this demand, higher-density wiring and an increase in the number of terminals have been eagerly sought for substrate modules and wiring boards which are provided with electronic components. Examples of such wiring boards include various kinds of build-up multilayer wiring boards such as one having, on an insulating core layer, a stacked layers structure obtained by alternately laminating insulating layers or dielectric layers, which are made of organic resin, and conductive layers. Examples of core layers include a thick layer in which a core material made of, e.g., glass cloth is impregnated with resin. Such a core layer prevents distortion, deformation, etc., of a substrate which might be caused during manufacturing.
However, when using the above core layer, a wiring board that is the final product becomes excessively thick, and this may not satisfy the recent demand for a reduction in thickness of wiring boards. In light of this, a method in which a wiring board is constituted only by thin resin layers and conductive layers other than a core layer can be employed. However, this method causes a large distortion in the resin layers due to the influence of heat applied during manufacturing and moisture. This will cause connection failures when an electrode pitch of, e.g., a semiconductor IC built into a wiring board is narrow. Also, a wiring board having a thickness of several tens of μm or less has been developed in order to help to attain a reduction in thickness and in height of wiring boards. However, the above wiring board tends to have a structural defect such as a warp or a crack during handling.
On the other hand, for example, JP2007-173622 A discloses a method including the steps of: forming a substrate stacked layers (laminated body) on a support substrate through a heat-peelable adhesive agent layer and an auxiliary conductive layer, and separating the substrate stacked layers from the support substrate at the boundary between the adhesive agent layer and the auxiliary conductive layer. Also, JP2005-243999 A discloses a method including the steps of: sequentially providing, on a support substrate, a base dielectric layer, a sheet base, a heat-peelable adhesion layer, and a dielectric layer; forming a stacked layers (laminated) structure of wiring thereon by a build-up process or the like; and then peeling the adhesion layer from the dielectric layer, thereby separating the stacked layers structure from the support substrate.
However, in the current manufacturing of a multilayer wiring board by a build-up process, there is a tendency for overlaying a large number of extremely thin resin layers. According to the inventor's finding, it has been found that performing heat treatment and pressure treatment many times on a support substrate leads to noticeable deterioration of an adhesive or adhesive agent layer (resin) that supports the support substrate in a fixed manner. For example, in the method disclosed in JP2007-173622 A, there is concern that a part of the deteriorated adhesive agent layer adheres to the stacked layers structure separated from the support substrate, and if this state remains, it becomes difficult for the subsequent wiring process, etc., to be performed. Also, the method disclosed in JP2005-243999 A shows a tendency concerning, in particular, noticeable deterioration of a sheet base. The residue of the sheet base adheres to the stacked layers structure, and thus becomes difficult to be removed, which negatively affects the subsequent wiring process, etc. Moreover, the sheet base and the adhesion layer which adhere to the base dielectric layer remain on the support substrate, and this makes the support substrate difficult to be recycled (reused).